An integrated circuit is typically formed on a semiconductor substrate or wafer, such as a silicon wafer, by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. The substrates are cut from a cylinder of silicon, commonly referred to as an ingot. A silicon ingot can be grown using the Czochralski process. The Czochralski process generally requires melting amorphous silicon or polysilicon and dipping a single crystal silicon into the melted silicon. The single crystal silicon allows the melted silicon to form large crystals. The single crystal silicon is then pulled from the melt to form the ingot. The ingot is sliced, such as with a wire saw, to create wafers. Wafers of various diameters, such as about 300 mm, can be created from an ingot formed in this way.
A batch of wafers from an ingot are then each double side polished to make the front and the back of the wafer parallel. The wafers can then be measured to determine their thickness. Once measured, the wafers are again polished to remove damage and correct the wafer's geometry, such as to eliminate waviness. Chemical mechanical polishing (CMP) is one polishing method used on the wafers. Post polishing, the wafers are again measured. The measurements obtained indicate the quality of the wafer. The post polishing measurements are used to categorize or grade the wafers, such as into prime grade, dummy grade, mechanical grade, etc. Each grade of wafer can be sold to manufacturers for producing various end products according to the manufacturer's needs.